Apparatuses for longitudinally pleating a lamina are known and have long been utilized in the art. For example, Canadian Patent 758,794 issued May 16, 1967, to Ives et al. discloses one such apparatus having convergent longitudinal sections to induce the pleats. The use of interdigitating circumferentially grooved rolls is known in the prior art, as illustrated by U.S. Pat. No. 4,517,714 issued May 21, 1985, to Sneed et al., which patent discloses a process for lateral tensioning of a lamina through the use of ring rolling. The prior art further teaches the use of a curved axis roll to laterally spread a lamina, as disclosed in U.S. Pat. No. 2,393,191 issued Jan. 15, 1946 to Robertson.
The prior art does not, however, teach an apparatus for longitudinally pleating a moving lamina by the use of rolls and without laterally tensioning the lamina. The prior art further does not teach an apparatus using multiple rolls or curved axis rolls to achieve substantial equalization of the paths of travel, taken in the machine direction, of any transversely corresponding points on the lamina.
It is an object of this invention to provide an apparatus for longitudinally pleating a moving lamina. It is further an object of this invention to provide an apparatus which achieves substantially equal machine direction travel of all points on the lamina as it passes through the apparatus. Finally, it is an object of this invention to provide an apparatus which can be used at relatively high speeds, e.g. at least about 180 meters per minute (600 feet per minute).